Fuel battery system

Abstract

To provide a fuel battery system capable of continuously operating a fuel battery efficiently.SOLUTION: A fuel battery system comprises: a heat storage unit having a fuel battery that generates an electric power by supplying hydrogen and a hot water storage tank 8 that stores waste heat of the fuel battery in hot water; a first consumption part 80 that consumes hot water stored in the hot water storage tank 8; and a plurality of adjustment mechanisms 56 that are provided corresponding to the hot water storage tanks 8 of the plurality of heat storage units, respectively, and that adjust an amount of hot water when supplying hot water from the hot water storage tank 8 to the first consumption part 80; and a state changing part 90 that changes the state of the plurality of adjusting mechanisms 56 in response to a request from the first consuming part 80 to cause supply of hot water from at least one of the plurality of heat storage units to the first consuming part 80.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system. [Background technology]

[0002] For example, in the fuel cell system disclosed in Patent Document 1, the exhaust heat from the fuel cell is stored in hot water in a hot water storage tank, and the hot water is used for hot water supply and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6647030 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when demand for hot water decreases, for example, in the summer, the hot water storage tank may have excess hot water, filling up with high-temperature hot water and potentially causing problems such as being unable to cool the fuel cell. In this case, it is conceivable to reduce the fuel cell's power output to suppress heat generation or to install a radiator to release the fuel cell's exhaust heat. When the fuel cell's power output decreases, the benefits of operating the fuel cell decrease. Furthermore, if the exhaust heat is released through a radiator, the running costs of operating auxiliary equipment such as a radiator fan increase, reducing the benefits of operating the fuel cell.

[0005] An object of the present invention is to provide a fuel cell system that can keep the fuel cell running efficiently. [Means for solving the problem]

[0006] The fuel cell system of the present invention is equipped with a heat storage unit having a fuel cell that generates electricity by supplying hydrogen-containing gas and oxygen-containing gas, and a hot water storage tank that stores the exhaust heat of the fuel cell in hot water, a first consumption unit that consumes the hot water stored in the hot water storage tank, a plurality of adjustment mechanisms provided corresponding to the hot water storage tanks of each of the plurality of heat storage units and that adjust the amount of hot water when supplying the hot water from the hot water storage tank to the first consumption unit, a detection unit provided corresponding to the hot water storage tanks of each of the plurality of heat storage units and that detects the amount of heat stored in the hot water storage tank, and a state change unit that causes the supply of hot water from at least one of the plurality of heat storage units to the first consumption unit by changing the state of the plurality of adjustment mechanisms in accordance with the request of the first consumption unit, and is characterized in that the state change unit is configured to change the state of the plurality of adjustment mechanisms in accordance with the amount of heat stored in each of the plurality of hot water storage tanks, and is configured to supply the hot water to the first consumption unit preferentially from the hot water storage tank with the largest amount of heat stored.

[0007] According to the present invention, when the first consumption unit consumes hot water, the states of the multiple adjustment mechanisms are changed, allowing the first consumption unit to receive hot water from at least one of the multiple heat storage units. This allows the hot water in the hot water storage tank with excess hot water to be shared with the first consumption unit. Therefore, even if the hot water storage tank is about to become full with high-temperature hot water, the hot water in the hot water storage tank is released to the first consumption unit, and new low-temperature water is supplied to the hot water storage tank. This makes it easier to maintain the power generation output of the fuel cell and continue to enjoy the benefits of operating the fuel cell. Furthermore, according to the present invention, hot water can be supplied to the first consumption unit from multiple hot water storage tanks according to the amount of heat stored. This allows the hot water to be supplied to the first consumption unit from multiple hot water storage tanks according to the amount of heat stored in that tank. Therefore, even if one of the multiple hot water storage tanks is about to become full with high-temperature hot water, the amount of heat stored in that hot water storage tank is preferentially released. As a result, it is easy to continue operating the fuel cell without suppressing the power generation output of the fuel cell in each heat storage unit. Thus, according to the present invention, a fuel cell system that can continue to operate the fuel cell efficiently is realized.

[0008] In the present invention, it is preferable that the first consumption unit includes a setting unit that sets the hot water supply temperature, and a heating unit that heats the hot water adjusted by the adjustment mechanism to the hot water supply temperature.

[0009] With this configuration, even if the temperature of the hot water from the hot water storage tank of the heat storage unit is lower than the set temperature required by the first consumption unit, the heating unit heats the hot water to the set temperature, allowing the user of the first consumption unit to receive hot water at the desired set temperature.

[0010] In the present invention, it is preferable that the adjustment mechanism mixes the hot water with water supplied from the water supply source without passing through the hot water storage tank, and the hot water after mixing by the adjustment mechanism is supplied to the heating section.

[0011] With this configuration, water from the water supply source can be preheated with hot water from the hot water storage tank before being heated in the heating section, making it possible to reduce energy consumption in the heating section.

[0012] In the present invention, it is preferable that a second consumption unit is provided which consumes the heat stored in the hot water storage tank by exchanging heat with the hot water flowing through a hot water circulation path in which the hot water taken out of the hot water storage tank returns to the hot water storage tank.

[0013] With this configuration, the heat stored in the hot water in the hot water storage tank is effectively utilized in the second consumption unit.

[0014] In the present invention, it is preferable that a plurality of first consumption units are provided, and the state change unit is configured to change the state of the plurality of adjustment mechanisms so as to connect the first consumption unit among the plurality of first consumption units that has a demand for hot water with the hot water storage tank that has a large amount of stored heat.

[0015] With this configuration, hot water is smoothly supplied to the first consumption units from the hot water storage tank with a large heat storage capacity in response to requests for hot water from each of the plurality of first consumption units.

[0016] In the present invention, it is preferable that the state change unit is configured to change the state of the multiple adjustment mechanisms so that the hot water from the hot water storage tank with the largest heat storage capacity among the multiple hot water storage tanks is supplied to the first consumption unit.

[0017] With this configuration, hot water can be supplied to the first consumption unit in descending order of the heat storage amount among the plurality of hot water storage tanks. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a block diagram showing the overall configuration of a cogeneration system. [Figure 2] 2 is a block diagram showing the relationship between a hot water storage tank, a regulating valve, and a hot water consuming device in the fuel cell system of the present disclosure. FIG. [Figure 3] FIG. 10 is a flowchart illustrating a state change of the regulator valve performed by a state change unit. [Figure 4] FIG. 10 is a block diagram showing an example of distributing hot water from a hot water storage tank to hot water consuming devices in other dwelling units. [Figure 5] FIG. 10 is a block diagram showing an example of distributing hot water from a hot water storage tank to hot water consuming devices in other dwelling units. [Figure 6] FIG. 10 is a block diagram showing an example of distributing hot water from a hot water storage tank to hot water consuming devices in other dwelling units. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment in which a fuel cell system according to the present invention is applied to a cogeneration system 1 will be described with reference to the drawings.

[0020] 1, the cogeneration system 1 includes a fuel cell unit U1, an exhaust heat recovery unit U2, a water purification unit U3, and a heat consumption unit U4. The fuel cell unit U1 and the exhaust heat recovery unit U2 correspond to "thermal storage units."

[0021] The fuel cell unit U1 is equipped with a fuel cell N, a cooling water circulation path 3, and a hydrogen-containing gas generation section P. A cooling water tank 16, a cooling water circulation pump 4, the fuel cell N, and a heat exchanger for exhaust heat recovery 2 are provided along the cooling water circulation path 3. Cooling water sucked from the cooling water tank 16 by the cooling water circulation pump 4 circulates through the fuel cell N and the heat exchanger for exhaust heat recovery 2, then circulates through the cooling water circulation path 3 and returns to the cooling water tank 16.

[0022] The hydrogen-containing gas generating section P is equipped with a reformer 11. The reformer 11 generates hydrogen-containing gas by causing a reforming reaction between hydrocarbon-based raw fuel gas (for example, natural gas-based city gas) and separately supplied steam by heating with a reforming burner 10. The raw fuel gas is supplied from a raw fuel gas supply path 9. The hydrogen-containing gas is supplied to the fuel electrode (not shown) of the fuel cell N.

[0023] The exhaust heat recovery unit U2 is equipped with an exhaust heat recovery circuit 5 and a hot water storage tank 8. The suction end and discharge end of the exhaust heat recovery circuit 5 are connected to the hot water storage tank 8. An exhaust heat recovery circulation pump 6 is provided midway along the exhaust heat recovery circuit 5. Hot water is sucked in from the bottom of the hot water storage tank 8 by the exhaust heat recovery circulation pump 6, and the hot water circulates through the exhaust heat recovery circuit 5 while passing through a composite heat exchanger 12 and an exhaust heat recovery heat exchanger 2 (described below) and is returned to the top of the hot water storage tank 8. Combustion exhaust gas from the reforming burner 10 and air electrode exhaust gas discharged from the air electrode (not shown) of the fuel cell N flow through the composite heat exchanger 12.

[0024] The hot water stored in the hot water storage tank 8 is supplied to a heat consuming unit U4 as hot water for hot water consumption devices 80 (such as a kitchen, bath, or sink) in the dwelling. The heat consuming unit U4 is equipped with a water heater 50 and a heating terminal 60 (such as a floor heating panel, a bath reheater, or a bathroom heater).

[0025] The water purification unit U3 purifies the cooling water flowing through the cooling water circulation path 3 and the condensed water generated in the combined heat exchanger 12.

[0026] The control device 7 is configured by software with a CPU and memory at its core for executing various processes, or by a combination of hardware and software.

[0027] [Fuel cell unit] The fuel cell unit U1 will be described. Since the fuel cell N is well known, detailed description and illustrations will be omitted. Simply described, the fuel cell N includes a solid polymer cell stack in which a plurality of cells, each having a solid polymer membrane as an electrolyte layer, are stacked. A hydrogen-containing gas is supplied from a hydrogen-containing gas generator P to the fuel electrode of each cell through a fuel gas supply path 13. Air (oxygen-containing gas) is supplied from a reaction air blower 14 to the oxygen electrode of each cell through an air supply path 15. The fuel cell N generates electricity through an electrochemical reaction between hydrogen contained in the hydrogen-containing gas and oxygen contained in the air. In other words, the fuel cell N generates electricity by supplying hydrogen.

[0028] Each cell in the cell stack is provided with a cooling water flow path. The cooling water circulating through the cooling water circulation path 3 cools each cell as it flows through each cooling water flow path in parallel. A cooling water tank 16 for storing cooling water is provided in the feed flow path portion of the cooling water circulation path 3 that runs from the exhaust heat recovery heat exchanger 2 to the fuel cell N. A cooling water circulation pump 4 draws cooling water from the cooling water tank 16 and pumps it to each cooling water flow path in the cell stack. The cooling water that flows out of each cooling water flow path in the cell stack is returned to the exhaust heat recovery heat exchanger 2 through the return flow path portion of the cooling water circulation path 3.

[0029] The hydrogen-containing gas generation unit P is equipped with a desulfurizer 17, a reformer 11, a transformer 18, and a carbon monoxide remover 19. The desulfurizer 17 desulfurizes the raw fuel gas supplied from the raw fuel gas supply channel 9. The reformer 11 generates a reformed gas containing hydrogen as a main component by a reforming reaction between the desulfurized raw fuel gas from the desulfurizer 17 and steam supplied from the reforming water channel 34. The transformer 18 converts carbon monoxide in the reformed gas from the reformer 11 into carbon dioxide using steam. The carbon monoxide remover 19 selectively oxidizes the carbon monoxide in the reformed gas from the transformer 18 with selective oxidation air that is separately supplied. As a result, a hydrogen-containing gas with a low carbon monoxide concentration is generated by the hydrogen-containing gas generation unit P.

[0030] An on-off valve 20 and a raw fuel supply amount adjustment valve 21 are provided in the raw fuel gas supply path 9. The on-off valve 20 opens and closes the raw fuel gas supply path 9. The raw fuel supply amount adjustment valve 21 adjusts the amount of raw fuel gas supplied.

[0031] Anode exhaust gas, with hydrogen remaining, is discharged from each anode of the fuel cell N. The anode exhaust gas is supplied to the reforming burner 10 as gas fuel through anode exhaust gas passage 22. Cathode exhaust gas is discharged from each cathode of the fuel cell N. The cathode exhaust gas is supplied to the aforementioned combined heat exchanger 12 through cathode exhaust gas passage 23.

[0032] Although not shown, a combustion air blower supplies combustion air to the reforming burner 10. The combustion exhaust gas from the reforming burner 10 is supplied to the aforementioned combined heat exchanger 12 through a combustion exhaust gas passage 24.

[0033] An inverter 41 for grid connection is provided on the power output side of the fuel cell N. The inverter 41 adjusts the power generated by the fuel cell N to the same voltage and frequency as the power supplied from a power source 42. The power source 42 is, for example, a single-phase three-wire 100 / 200V power source, and is connected to a distribution board 43, to which power loads 44 such as televisions, refrigerators, and washing machines are connected. Therefore, the power from the power source 42 and the power generated by the fuel cell N are supplied to the power loads 44 via the distribution board 43 at the same voltage and frequency.

[0034] [Waste heat recovery unit] The exhaust heat recovery unit U2 will now be described. In the exhaust heat recovery circulation path 5, a composite heat exchanger 12 is provided in a return flow path portion extending from the bottom of the hot water storage tank 8 to the exhaust heat recovery heat exchanger 2.

[0035] An exhaust heat recovery circulation pump 6 is provided in the return flow path portion of the exhaust heat recovery circulation path 5, upstream of the combined heat exchanger 12. The exhaust heat recovery circulation pump 6 draws hot water from the bottom of the hot water storage tank 8. In other words, the hot water drawn from the bottom by the exhaust heat recovery circulation pump 6 flows through the exhaust heat recovery circulation path 5 while being heated in the combined heat exchanger 12 and the exhaust heat recovery heat exchanger 2, and is returned to the top of the hot water storage tank 8. In this way, the hot water storage tank 8 stores the exhaust heat of the fuel cell N in the hot water. Temperature stratification of the hot water is formed in the hot water storage tank 8, with the hot water being at a higher temperature at the top of the tank.

[0036] The hot water storage tank 8 is equipped with water temperature measuring units S for detecting the temperature of the stored hot water, including an upper water temperature measuring unit S1, an upper middle water temperature measuring unit S2, a top / bottom center water temperature measuring unit S3, a lower middle water temperature measuring unit S4, and a lower water temperature measuring unit S5. The upper water temperature measuring unit S1 is provided at the top of the hot water storage tank 8. The upper middle water temperature measuring unit S2 is provided in an upper middle section between the top of the hot water storage tank 8 and the top / bottom center of the hot water storage tank 8. The top / bottom center water temperature measuring unit S3 is provided in the top / bottom center of the hot water storage tank 8. The lower middle water temperature measuring unit S4 is provided in a lower middle section between the top / bottom center of the hot water storage tank 8 and the bottom of the hot water storage tank 8. The lower water temperature measuring unit S5 is provided at the bottom of the hot water storage tank 8. The lower water temperature measuring unit S5 is located above the bottom of the hot water storage tank 8. The water temperature measuring units S have a thermometer such as a temperature sensor. The water temperature measuring section S corresponds to the "detection section."

[0037] Temperature stratification of hot water is formed in the hot water storage tank 8. For this reason, it is possible to calculate the amount of heat stored in the hot water storage tank 8 based on the detection results from the upper hot water temperature measuring unit S1 to the lower hot water temperature measuring unit S5.

[0038] [Water purification unit] The water purification unit U3 will now be described. The water purification unit U3 is equipped with a purification circuit 31. A water purification unit 30, a recovered water tank 32, and a recovered water circulation pump 33 are provided along the purification circuit 31. The water purification unit 30 purifies the water flowing through the purification circuit 31. The recovered water circulation pump 33 circulates the water in the recovered water tank 32 through the purification circuit 31. The water purification unit 30 uses ion exchange resins or the like to remove impurities (sulfate ions, ammonium ions, etc.) contained in the water flowing through the purification circuit 31, thereby converting it into pure water.

[0039] In addition, a recovery water channel 25 is connected in communication with the recovered water tank 32. The recovery water channel 25 is connected to the combined heat exchanger 12 and the recovered water tank 32. In the combined heat exchanger 12, heat exchange takes place between the combustion exhaust gas from the reforming burner 10 and the hot water circulating through the exhaust heat recovery circuit 5, and the water vapor mixed with the combustion exhaust gas condenses to generate condensed water. The condensed water generated in the combined heat exchanger 12 falls into the recovered water tank 32 through the recovery water channel 25.

[0040] A cooling water tank 16 is provided in the middle of the purification circulation path 31. The cooling water tank 16 is located above the recovered water tank 32.

[0041] A reforming water channel 34 branches off from the purification circulation channel 31 at a location between the recovered water circulation pump 33 and the cooling water tank 16. The reforming water channel 34 is connected to the reformer 11. A purification on-off valve 35 is provided in the purification circulation channel 31 downstream of the branch point. In addition, a reforming on-off valve 36 is provided in the reforming water channel 34.

[0042] When the recovered water circulation pump 33 operates while the fuel cell N is operating, the purification on-off valve 35 is closed, and the reforming on-off valve 36 is open, the water in the recovered water tank 32 is purified in the purification section and turned into pure water. The pure water is then supplied to a steam generation section (not shown) of the reformer 11 through the reforming water passage 34, and steam for reforming the raw fuel gas is generated.

[0043] In addition, a recovery water channel 25 is connected in communication with the recovered water tank 32. The recovery water channel 25 is connected to the combined heat exchanger 12 and the recovered water tank 32. When heat is exchanged in the combined heat exchanger 12 between the combustion exhaust gas from the reforming burner 10 and the hot water circulating through the exhaust heat recovery circuit 5, condensed water is generated. The condensed water generated in the combined heat exchanger 12 falls into the recovered water tank 32 through the recovery water channel 25. The condensed water recovered in the recovered water tank 32 is purified in the water purifier 30 and sent again to the steam generation section of the reformer 11 through the reforming water channel 34. The water stored in the recovered water tank 32 circulates in this order through the reforming water channel 34, the reformer 11, the combustion exhaust gas channel 24, the combined heat exchanger 12, the combustion exhaust gas channel 24, and the recovered water tank 32, thereby achieving so-called water independence. In order to generate condensed water in the combined heat exchanger 12, the temperature of the water drawn from the bottom of the hot water storage tank 8 into the exhaust heat recovery circuit 5 is preferably 10 to 35°C, for example.

[0044] When the recovered water circulation pump 33 is activated while the fuel cell N is not operating, the purification on-off valve 35 is open, and the reforming on-off valve 36 is closed, the water in the recovered water tank 32 is purified in the purification section and turned into pure water, and this pure water is supplied to the cooling water tank 16. Then, water overflowing from the cooling water tank 16 falls into the recovered water tank 32.

[0045] At this time, when the water in the cooling water tank 16 falls onto the surface of the recovered water in the recovered water tank 32, a degassing action is performed by the impact of the fall, and the carbon dioxide contained in the recovered water is separated as a gas into the air. An exhaust path is provided in the upper space of the recovered water tank 32, and this exhaust path is open to the atmosphere. The carbon dioxide separated by the degassing action is discharged to the outside through the exhaust path.

[0046] [Fuel cell unit operation control] A brief description will be given of the control actions taken by the operation control unit 71 when performing the cogeneration operation. In the cogeneration operation, the operation control unit 71 activates the cooling water circulation pump 4 and the exhaust heat recovery circulation pump 6, opens the on-off valve 20, and controls the raw fuel supply amount adjustment valve 21 to adjust the amount of raw fuel gas supplied, and controls the reaction air blower 14 to adjust the amount of air supplied, in order to adjust the power generation output of the fuel cell N according to the power load 44. In addition, the operation control unit 71 activates the recovered water circulation pump 33 with the purification on-off valve 35 closed and the reforming on-off valve 36 open.

[0047] In the combined heat and power operation, the power output of the fuel cell N is converted by the inverter 41 to the same voltage and frequency as the power source 42 and consumed by the power load 44. As shown in Figure 1, cooling water circulates through the cooling water circuit 3 around the fuel cell N and the exhaust heat recovery heat exchanger 2, and hot water in the hot water storage tank 8 circulates through the combined heat exchanger 12 and the exhaust heat recovery heat exchanger 2 and the exhaust heat recovery circuit 5.

[0048] When an instruction to stop the combined heat and power supply operation is given by an operation unit (not shown) or the like, the operation control unit 71 closes the on-off valve 20 and the raw fuel supply amount adjustment valve 21, stops the reaction air blower 14, and stops the cooling water circulation pump 4, the exhaust heat recovery circulation pump 6, and the recovered water circulation pump 33, thereby stopping the fuel cell N.

[0049] [Heat consumption unit] The heat consuming unit U4 will be described. The heat consuming unit U4 includes a water heater 50 and a heating terminal 60.

[0050] The water heater 50 heats the hot water taken out from the hot water storage tank 8 via the water supply passage 38 to a predetermined hot water supply temperature, and then supplies the hot water to a hot water consumption device 80 (such as a kitchen, a bath, or a washbasin) located outside the water heater 50. The hot water supply setting unit 73 (setting unit) sets the hot water supply temperature to the hot water consumption device 80.

[0051] The hot water consumption device 80 consumes the hot water stored in the hot water storage tank 8. The heating terminal 60 receives the heat of the hot water stored in the hot water storage tank 8 through the heat dissipation heat exchanger 61 and consumes it. The water heater 50 corresponds to the "heating unit." The hot water consumption device 80 corresponds to the "first consumption unit." The heating terminal 60 corresponds to the "second consumption unit."

[0052] The water heater 50 in this embodiment is provided with a hot water supply pipe 51 connected to the hot water storage tank 8, a heat exchanger 52 provided midway along the pipe 51, and a burner 53 serving as a heat source. The pipe 51 passes through the inside of the heat exchanger 52. Raw fuel gas supplied from the raw fuel gas supply path 9 is burned in the burner 53. Heat exchange occurs in the heat exchanger 52 between the heat of the combustion flame in the burner 53 and the hot water in the pipe 51, and the hot water in the pipe 51 is heated.

[0053] A first water supply passage 38A, which supplies water from a water supply source such as a tap, is connected to the bottom of the hot water storage tank 8. A hot water supply passage 39, which delivers hot water to a hot water consuming section (not shown) such as a kitchen or a bathtub, is connected to the top of the hot water storage tank 8. The first water supply passage 38A supplies tap water supplied from an external water pipe W to the hot water storage tank 8. The hot water storage tank 8 can supply hot water to a water heater 50 via the hot water supply passage 39.

[0054] A second water supply passage 38B is connected to the hot water supply passage 39. Like the first water supply passage 38A, water flows through the second water supply passage 38B from a water supply source such as a tap. The water supply passage 38 branches into the first water supply passage 38A and the second water supply passage 38B. An adjustment valve 56 is provided at the confluence of the hot water supply passage 39 and the second water supply passage 38B. The adjustment valve 56 is provided corresponding to each of the hot water storage tanks 8 of the multiple exhaust heat recovery units U2. In addition, a water temperature measuring unit 55 is provided in the water supply passage 38. The adjustment valve 56 corresponds to the "adjustment mechanism."

[0055] Furthermore, the water temperature measuring unit 55 has a thermometer such as a temperature sensor, etc. The thermometer measures the temperature of the water flowing through the second water supply passage 38B.

[0056] Relatively high temperature hot water stored in hot water storage tank 8 is discharged from hot water supply path 39. Relatively high temperature hot water discharged from hot water storage tank 8 via hot water supply path 39 and relatively low temperature water supplied via second water supply path 38B flow into adjustment valve 56. State change unit 90 controls the operation of adjustment valve 56 so that the temperature of the hot water circulating from adjustment valve 56 to hot water supply path 39 downstream becomes the target hot water outlet temperature (e.g., 30 to 35°C).

[0057] Adjustment valve 56 is, for example, a four-way valve, and controls the flow rate of hot water through hot water supply path 39 and the combined flow rate of water from second water supply path 38B. Adjustment valve 56 may also be a rotary valve, solenoid valve, or the like. Adjustment valve 56 adjusts the opening of hot water supply path 39 and second water supply path 38B in response to a signal from state change unit 90. In other words, state change unit 90 controls the opening rate of communication between second water supply path 38B and hot water supply path 39 using adjustment valve 56 based on the target hot water outlet temperature.

[0058] On the other hand, when hot water supply to the water heater 50 is stopped, the state change unit 90 shuts off the hot water supply path 39 on the hot water storage tank 8 side, and controls the valve position of the adjustment valve 56 so that the second water supply path 38B side is fully open. In other words, when hot water supply to the water heater 50 is stopped, the valve position of the adjustment valve 56 becomes a valve position that allows water from the second water supply path 38B to flow into the pipe 51.

[0059] In this way, the adjustment valve 56 adjusts the amount of hot water supplied from the hot water storage tank 8 to the hot water consumption device 80. Then, the water heater 50 heats the hot water adjusted by the adjustment valve 56 to the hot water supply temperature.

[0060] A hot water consumption circuit 62 is connected to both the top and bottom of the hot water storage tank 8. A consumption circulation pump 63 and a heat dissipation heat exchanger 61 are provided midway along the hot water consumption circuit 62. When the consumption circulation pump 63 is driven, hot water is sucked from the top of the hot water storage tank 8 into the hot water consumption circuit 62 by the consumption circulation pump 63, and the hot water is returned to the bottom of the hot water storage tank 8 via the heat dissipation heat exchanger 61.

[0061] A heat medium circulation path 64 is connected to the heat dissipation heat exchanger 61. A heat medium circulation pump 65 is provided midway along the heat medium circulation path 64. The heat medium circulates between the heat dissipation heat exchanger 61 and the heating terminal 60 through the heat medium circulation path 64. In the heat dissipation heat exchanger 61, the hot water in the hot water storage tank 8 is cooled, and the heat medium in the heat medium circulation path 64 is heated.

[0062] The heating control unit 72 is configured to execute a hot water consumption process that controls the operation of the consumption circulation pump 63 in a manner that circulates hot water at a set target flow rate through the hot water consumption circuit 62, and when executing the hot water consumption process, to execute a heating circulation process that circulates the heat medium through the heat medium circulation path 64.

[0063] When floor heating, bath reheating, bathroom heating, etc. are operated, the heating control unit 72 activates the consumption circulation pump 63 and heat medium circulation pump 65 of the heating terminal 60. This consumes the heat of the hot water stored in the hot water storage tank 8.

[0064] In this way, the heating terminal 60 consumes the heat stored in the hot water storage tank 8 by undergoing heat exchange with the hot water flowing through the hot water consumption circuit 62 (hot water circulation path) in which the hot water taken out of the hot water storage tank 8 returns to the hot water storage tank 8.

[0065] [Control of supplying hot water from the hot water storage tank to other dwelling units] As described above, the exhaust heat of the fuel cell N is stored in the hot water in the hot water storage tank 8, and the hot water in the hot water storage tank 8 is used to preheat the water supplied to the water heater 50. However, if the water heater 50 is not used much while the fuel cell N continues to operate, the amount of heat stored in the hot water storage tank 8 continues to increase, and not only the hot water in the upper part of the hot water storage tank 8 but also the hot water in the lower part of the hot water storage tank 8 becomes hot. If the hot water at the bottom of the hot water storage tank 8 becomes hot (for example, 35°C or higher), this hot water flows into the exhaust heat recovery heat exchanger 2, making it impossible to cool the cooling water in the cooling water circulation path 3. As a result, the cells of the fuel cell N cannot be properly cooled, which may lead to problems such as a breakdown of the fuel cell N.

[0066] Furthermore, when the hot water at the bottom of the hot water storage tank 8 becomes hot and flows into the combined heat exchanger 12, sufficient heat exchange does not occur between the combustion exhaust gas from the reforming burner 10 and the hot water circulating through the exhaust heat recovery circuit 5, making it difficult for condensed water to be generated from the steam mixed with the combustion exhaust gas. As a result, the steam supplied to the reformer 11 from the reforming water channel 34 is released directly into the atmosphere, and so-called water independence is no longer achieved.

[0067] One possible solution to this problem would be to reduce the power generation output of the fuel cell N to suppress the amount of heat generated, but the reduction in power generation output would reduce the benefits of operating the fuel cell unit U1. Also, while it would be possible to provide a radiator on the outgoing path of the exhaust heat recovery circulation path 5, an increase in the power required to operate auxiliary equipment such as the radiator's cooling fan would reduce the benefits of operating the fuel cell unit U1.

[0068] FIG. 1 shows a configuration in which a cogeneration system 1, a water heater 50, and a hot water consumption device 80 are provided in one dwelling unit. Meanwhile, FIG. 2 shows a configuration in which a cogeneration system 1, a water heater 50, and a hot water consumption device 80 are provided in each of a plurality of dwelling units. In other words, the plurality of heat storage units (fuel cell unit U1 and exhaust heat recovery unit U2) shown in FIG. 2 are arranged in, for example, an apartment building, a plurality of detached houses, a two-family home, or the like. Note that FIG. 2 also shows the hot water storage tank 8 of the cogeneration system 1. As another means for solving the above problem, this embodiment is configured to allow hot water in the hot water storage tank 8 to be shared with the water heater 50 and the hot water consumption device 80 in a dwelling unit (other dwelling unit) different from the dwelling unit in which the hot water storage tank 8 is located. As shown in FIGS. 1 and 2, the second water supply line 38B is connected to the hot water supply line 39 of each dwelling unit via a control valve 56.

[0069] The cogeneration systems 1 in each dwelling unit shown in Figure 2 are configured to allow power to be shared between the dwelling units. Each fuel cell unit U1 in the cogeneration system 1 in each dwelling unit functions as a distributed power generation device. In other words, the cogeneration systems 1 in each dwelling unit shown in Figure 2 form a group that allows the sharing of generated power with each other. Specifically, power is supplied from the fuel cell unit U1 in a dwelling unit that is generating surplus power to a load in a dwelling unit that is short of power.

[0070] As shown in Fig. 2, the state changing unit 90 is configured to be able to control each of the regulating valves 56 in each dwelling unit. The state changing unit 90 is also configured to be able to acquire the detection results of each of the hot water temperature measuring units S in each dwelling unit. The state changing unit 90 calculates the amount of heat stored in each of the hot water storage tanks 8 based on the detection results of each of the hot water temperature measuring units S in each dwelling unit. The state changing unit 90 then selects the hot water storage tank 8 with the highest amount of heat stored among the hot water storage tanks 8 in each dwelling unit, and supplies hot water from the hot water storage tank 8 with the highest amount of heat stored to the hot water consumption device 80 to be supplied.

[0071] Explained based on the flowchart in Figure 3, the state change unit 90, in response to a request from the hot water consumption device 80 (start), acquires the measurement results of the hot water temperature measurement unit S in each hot water storage tank 8 in each dwelling unit (step #01). Then, the state change unit 90 calculates the amount of heat stored in each hot water storage tank 8 based on the measurement results of the hot water temperature measurement unit S (step #02), and supplies hot water from the hot water storage tank 8 with the largest amount of stored heat to the hot water consumption device 80 to be supplied (step #03).

[0072] The hot water temperature measuring units S are provided corresponding to the plurality of hot water storage tanks 8, and detect the amount of heat stored in the hot water storage tanks 8. The state changing unit 90 is configured to change the state of the plurality of regulating valves 56 in accordance with the amount of heat stored in each of the plurality of hot water storage tanks 8. In addition, the state changing unit 90 is configured to supply hot water to the hot water consuming device 80 by giving priority to the hot water storage tank 8 with the greatest amount of stored heat.

[0073] 4 and 5, the hot water storage tanks 8 are designated 8A, 8B, 8C, and 8D in descending order of heat storage capacity. Also, in Figures 4 and 5, the control valve 56 connected to the hot water supply path 39 of the hot water storage tank 8A with the highest heat storage capacity is designated as the first control valve 56A, the control valve 56 connected to the piping 51 of the target hot water heater 50 is designated as the second control valve 56B, and the control valve 56 directly connected to a water supply source such as a tap is designated as the third control valve 56C. The third control valve 56C is located at the bottom of the drawing.

[0074] 4 and 5, closed control valves 56 are shaded in black. Also, in Figures 4 and 5, the hot water flowing from the hot water storage tank 8A to the hot water consumption device 80 to be supplied is shown by a thick solid line, and the water flowing from the water supply to the hot water consumption device 80 without passing through the hot water storage tank 8A is shown by a thick dashed line.

[0075] In the example shown in Figure 4, hot water is supplied from the topmost hot water storage tank 8A to the third hot water consumption device 80 from the top. Therefore, the topmost control valve 56 on the page is the first control valve 56A, and the third control valve 56 on the page is the second control valve 56B. The second control valve 56B is located between the first control valve 56A and the third control valve 56C. Therefore, in the example shown in Figure 4, water supplied from the water supply source of the city water supply via the third control valve 56C without passing through the hot water storage tank 8 and hot water supplied from the hot water storage tank 8A via the first control valve 56A are mixed by the second control valve 56B. Then, the hot water mixed by the second control valve 56B is supplied to the water heater 50 and the hot water consumption device 80.

[0076] In the example shown in Figure 5, hot water is supplied from the hot water storage tank 8A, which is third from the top on the page, to the hot water consumption device 80, which is uppermost on the page. Therefore, the third control valve 56 from the top on the page is the first control valve 56A, and the uppermost control valve 56 on the page is the second control valve 56B. The second control valve 56B is located on the opposite side of the first control valve 56A from the third control valve 56C side. Therefore, in the example shown in Figure 5, water supplied from the water supply source of the city water supply via the third control valve 56C without passing through the hot water storage tank 8 and hot water supplied from the hot water storage tank 8A are mixed by the first control valve 56A. Then, the hot water mixed by the first control valve 56A is supplied to the water heater 50 and the hot water consumption device 80.

[0077] In this way, the state changing unit 90 operates the first adjustment valve 56A so that the hot water supply path 39 of the hot water storage tank 8A and the second water supply path 38B communicate with each other, and operates the second adjustment valve 56B so that the piping 51 connected to the hot water consumption device 80 to be supplied communicates with the second water supply path 38B. In other words, the state changing unit 90 is configured to change the states of the multiple adjustment valves 56 so that a hot water consumption device 80 that requests hot water communicates with the hot water storage tank 8 that has the largest amount of stored heat. In this way, the state changing unit 90 is configured to change the states of the multiple adjustment valves 56 so that hot water from the hot water storage tank 8 that has the largest amount of stored heat is supplied to the hot water consumption device 80.

[0078] Furthermore, the control valve 56 mixes water supplied from the water supply source without passing through the hot water storage tank with hot water supplied from the hot water storage tank 8. As a result, the hot water mixed by the control valve 56 is supplied to the water heater 50. This allows the water from the water supply source to be preheated by the hot water from the hot water storage tank 8 before being heated in the water heater 50, thereby reducing energy consumption in the water heater 50. Furthermore, it becomes easier to continue operating the fuel cell N without suppressing the power generation output of the fuel cell N in each fuel cell unit U1.

[0079] In this way, the state change unit 90 changes the state of the multiple control valves 56 in accordance with the request of the hot water consumption device 80, thereby causing hot water to be supplied from at least one of the multiple exhaust heat recovery units U2 to the hot water consumption device 80.

[0080] [Another embodiment] The present invention is not limited to the configurations exemplified in the above-described embodiments, and other representative embodiments of the present invention will be exemplified below.

[0081] (1) The fuel cell unit U1 disclosed in the above embodiment has a hydrogen-containing gas generator P. However, the present invention is not limited to this embodiment, and the fuel cell unit U1 may not be provided with a hydrogen-containing gas generator P and may be able to receive a direct supply of hydrogen from the outside.

[0082] (2) The present invention is not limited to the above-described embodiment, and may be configured to include a communication passage 100 communicating with each of the hot water supply passages 39 of the plurality of hot water storage tanks 8 and each of the pipes 51 connected to the plurality of hot water consumption devices 80, as shown in Fig. 6. In this case, an on-off valve 101 may be provided at the boundary between the communication passage 100 and each of the hot water supply passages 39. Alternatively, a second water supply passage 38B may merge with the boundary between the communication passage 100 and each of the pipes 51, and an adjustment valve 102 may be provided at this junction. The state change unit 90 may open the on-off valve 101 in the hot water supply passage 39 of the hot water storage tank 8 with the largest amount of stored heat, and mix the hot water with the tap water at the adjustment valve 102 in the pipe 51 connected to the hot water consumption device 80 to be supplied.

[0083] (3) The heating terminal 60 (second consumption unit) may not be provided.

[0084] (4) As described above in step #03 of Fig. 3, the state change unit 90 is configured to change the states of the multiple regulating valves 56 so that hot water from the hot water storage tank 8 with the largest amount of stored heat among the multiple hot water storage tanks 8 is supplied to the hot water consumption device 80. Without being limited to this embodiment, the state change unit 90 may be configured to supply hot water to the hot water consumption device 80 by giving priority to the hot water storage tank 8 with the largest amount of stored heat among the multiple hot water storage tanks 8. For this reason, the hot water may be supplied to the hot water consumption device 80 from the hot water storage tank 8 with the second largest amount of stored heat among the multiple hot water storage tanks 8.

[0085] (5) In the above embodiment, hot water is supplied from one hot water storage tank 8 in one dwelling unit to one hot water consumption device 80 in another dwelling unit. This embodiment is not limited to this, and a configuration in which hot water is simultaneously supplied from one hot water storage tank 8 in one dwelling unit to each of the hot water consumption devices 80 in multiple other dwelling units may also be used. Furthermore, a configuration in which hot water is simultaneously supplied from each of the hot water storage tanks 8 in multiple dwelling units to one hot water consumption device 80 may also be used.

[0086] (6) In the above embodiment, a polymer electrolyte fuel cell is used as the fuel cell N, but the present invention can also be implemented in the same manner when the fuel cell N includes a solid oxide fuel cell.

[0087] The configurations disclosed in the above-described embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with the configurations disclosed in other embodiments, unless a contradiction arises. Furthermore, the embodiments disclosed in this specification are merely examples, and the present invention is not limited to these, and can be modified as appropriate within the scope of the present invention. [Industrial Applicability]

[0088] The present invention is applicable to fuel cell systems. [Explanation of symbols]

[0089] 8: Hot water tank 50: Water heater (heating unit) 56: Control valve (control mechanism) 60: Heating terminal (secondary consumption unit) 62: Hot water consumption circuit (hot water circulation path) 80:Hot water consumption device (first consumption part) 90: State change section 102: Control valve N: Fuel cell S: Water temperature measurement unit (detection unit) U1: Fuel cell unit (heat storage unit) U2: Exhaust heat recovery unit (heat storage unit) U4: Heat dissipation unit

Claims

1. a heat storage unit including a fuel cell that generates electricity by supplying a hydrogen-containing gas and an oxygen-containing gas, and a hot water storage tank that stores exhaust heat from the fuel cell in hot water; a first consumption unit that consumes the hot water stored in the hot water storage tank; a plurality of adjustment mechanisms provided corresponding to the hot water storage tanks of the plurality of heat storage units, each adjusting the amount of hot water when the hot water is supplied from the hot water storage tank to the first consumption unit; a detector provided corresponding to each of the hot water storage tanks of the plurality of heat storage units, the detector detecting the amount of heat stored in the hot water storage tank; a state changing unit that changes the state of the plurality of adjustment mechanisms in response to a request from the first consumption unit, thereby causing the supply of hot and cold water from at least one of the plurality of heat storage units to the first consumption unit to occur; The state change unit is configured to change the state of the multiple adjustment mechanisms according to the amount of heat stored in each of the multiple hot water storage tanks, and is configured to supply hot water to the first consumption unit by giving priority to the hot water storage tank with the largest amount of heat stored.

2. 2. The fuel cell system according to claim 1, wherein the first consumption unit is provided with a setting unit that sets the hot water supply temperature and a heating unit that heats the hot water adjusted by the adjustment mechanism to the hot water supply temperature.

3. The adjusting mechanism mixes the hot water with water supplied from a water supply source without passing through the hot water storage tank, 3. The fuel cell system according to claim 2, wherein the hot and cold water mixed by the adjusting mechanism is supplied to the heating section.

4. A fuel cell system as described in claim 1, which is provided with a second consumption unit that consumes the heat stored in the hot water storage tank by undergoing heat exchange with the hot water flowing through a hot water circulation path where the hot water taken out of the hot water storage tank returns to the hot water storage tank.

5. A plurality of the first consumers are provided, The fuel cell system of claim 1, wherein the state change unit is configured to change the state of the plurality of adjustment mechanisms so as to connect the first consumption unit among the plurality of first consumption units that has a demand for hot water with the hot water storage tank that has a large amount of stored heat. the hot water storage tank

6. The fuel cell system described in claim 1, wherein the state change unit is configured to change the state of the multiple adjustment mechanisms so as to supply the hot water from the hot water storage tank with the largest heat storage capacity among the multiple hot water storage tanks to the first consumption unit.

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